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SEER Inquiry System - Report
Produced: 11/22/2025 2:12 AM
Question 20140013
Inquiry Details
References:
ICD-O-3
Question:
Primary site--Brain and CNS: How should primary site be coded for a medulloblastoma described as a "posterior fossa mass" and "centered within the fourth ventricle"? See discussion.
Discussion:
The associated site code for medulloblastoma in the ICD-O-3 is C716. However, the SEER Manual specifically instructs to ignore the associated site code if a different primary site is noted. Although most medulloblastomas appear to arise in the cerebellum, when described as "centered within the fourth ventricle" can we assume that is the primary site and not simply invasion of the fourth ventricle from the cerebellum?
Answer:
Code the primary to C717 for this case.
Code the primary site according to the origin of a particular medulloblastoma when it differs from the site code listed in ICD-O-3. The description "centered within the fourth ventricle" suggests that this medulloblastoma originated in the fourth ventricle.
Cancer Site Category:
Brain and CNS
Data Item Category:
Primary site
Other Category:
N/A
Year:
2014
